In order to gain an understanding of the nature of hormonal dependency and autonomy of breast cancers, a basic understanding of the mechanism of action of hormones at the cellular and subcellular level will be necessary. Control of growth and function of the normal mammary gland and mammary tumors results from multihormonal interactions. It is the purpose of this proposal to investigate the role of insulin on experimental mammary tumors. Studies will be conducted with DMBA- induced tumors, which we have shown to be insulin-dependent, and with the R3230AC mammary adenocarcinoma, which we have shown to be autonomous but insulin-responsive. Data from our laboratory indicate that alterations in growth, enzyme activities and utilization of glucose in vitro of these tumors were correlated in diabetic or in insulin-treated animals. To investigate in greater depth the mechanisms whereby insulin interacts with these neoplasms, we will examine and characterize the insulin receptors in the plasma membranes of these tumors, utilizing both isolated whole cells and isolated plasma membrane preparations, and will determine the specificity of binding, the levels of binding and the influence of hormonal perturbation of the host animal, e.g., diabetes, estrogen therapy, etc., on the properties of insulin binding. It is also planned to examine the sequence of events that follow the hormone- cell interaction by investigating the levels of second messengers (cAMP, cGMP) and those enzymes that influence the levels of cyclic nucleotides e.g., adenyl cyclase, cAMP phosphodiesterase. Additional studies, based on our earlier findings, of glucose metabolism in vivo and in vitro by these tumors will be conducted after hormonal perturbation of the host to seek correlations between tumor growth and biochemistry. Comparable studies of normal mammary glands, at various stages of differentiation, are planned so as to identify those defects or alterations expressed in the neoplasms.